1. Field of the Invention
The present invention relates generally to an apparatus for reproducing information recorded on an optical disc, and more particularly to an information reproducing apparatus of this kind which performs the processing for optically reading and reproducing information recorded on an optical disc being rotated, while correcting the time base of the read information.
2. Description of the Related Art
Attempts have been made for reproducing digital information recorded on an optical disc in a high quality, particularly in the field of audio-related applications. One of such attempts involves a technique of reproducing a read signal at a high resolution. Specifically, a read signal is sampled at a high rate and converted to a digital signal using a large number of quantization bits. Another attempt involves an extension of a frequency band in which a read signal is reproduced. In other words, the latter attempt aims at faithfully outputting an audio signal in a high frequency band, as well, which has been essentially ignored.
Other than the attempts mentioned above, there are also indispensable factors for high quality reproduction. One of these factors is a so-called time base correction, i.e., a reduction in fluctuations (jitter) of a read signal on the time base. In the prior art, such time base correction has also been employed, and a variety of approaches have been proposed therefor.
However, a majority of such proposals rely on an idea of macroscopically performing the time base correction, and tend to treat lightly microscopical time base correction. For this reason, a jitter component escaping from the macroscopic time base correction is likely to remain and affects the quality of reproduced information. Therefore, there is yet room for improvement in the time base correction. Particularly for audio devotees who continue insatiable pursuit of ever higher sound quality, even a slight improvement in sound quality is extremely useful, so that a search for complete accomplishment of the time base correction is important.
Specifically, high frequency components in a driving signal supplied to a spindle motor of direct-current driving type is the cause of preventing highly stable control for the spindle motor.
Eventually, such a microscopic defect may be an obstacle to time base correction for a read signal and accordingly to reproduction of high quality information.
Therefore, the present invention has been made in view of the problem mentioned above, and its object is to provide an apparatus for reproducing information recorded on an optical disc which is capable of favorably correcting the time base of a read signal in a simple configuration.
It is another object of the present invention to provide an apparatus for reproducing information recorded on an optical disc which is capable of precisely removing a jitter component produced when a driving signal is supplied to a spindle motor.
An apparatus for reproducing information recorded on an optical disc according to the present invention comprises a spindle motor for rotating an optical disc, reading means for optically reading a recorded signal on the optical disc to generate a read signal corresponding to the recorded signal, digital converting means for digitizing the read signal to reproduce an encoded signal, and control means for supplying the spindle motor with driving power, where the control means has unnecessary component removing means for removing high frequency components from the driving power.